Bonded multi-layer graphite heat pipe

ABSTRACT

A passive heat pipe structure used in a wearable device includes a multilayer stack of graphite sheets, each sheet having a plane high thermal conductivity oriented along a first axis and a plane of lower thermal conductivity along a second axis different from the first axis. The stack has a three-dimensional shape including a length and a width where the length is longer than the width and the first axis aligns parallel to said length, the multilayer stack having a height less than the width. A plurality of bonding layers interspersed between each sheet of the multilayer stack, each bonding layer thermally coupling each sheet to a respective adjacent sheet. The bonding layers may comprise metal layers or adhesive layers.

BACKGROUND

A see-through, mixed reality display device system enables a user toobserve digital information overlaid on the physical scenery. To enablehands-free user interaction, a see-through, mixed reality display devicesystem may further be equipped with an eye tracker, sensors anddisplays, all of which are sensitive to mis-alignment if the opticalplatform or frame on which they are mounted distorts. Like all deviceswhich include electronic components, the components produce heat whichmust be redistributed to areas of the device that are not adjacent tothe components. This ensures proper component operation and opticalplatform stability.

SUMMARY

The technology briefly described comprises a passive pseudo-heat pipestructure used in a wearable device. The structure includes a multilayerstack of graphite sheets, each sheet having a plane high thermalconductivity oriented along a first axis and a plane of lower thermalconductivity along a second axis different from the first axis. The axisof each layer are aligned. The stack has a three-dimensional shapeincluding a length and a width where the length is longer than the widthand the first axis aligns parallel to said length, the multilayer stackhaving a height less than the width. A plurality of bonding layersinterspersed between each sheet of the multilayer stack, each bondinglayer thermally coupling each sheet to a respective adjacent sheet. Thebonding layers may comprise metal layers or adhesive layers. The pipestructure may be used in an optical mounting structure having heatproducing control circuitry and temple arms adapted to secure themounting structure to the head of a wearer. In this embodiment, a bondedstack of graphite layers is thermally bonded to at least any or some ofa device's heat emitting components circuitry and the optical mountingstructure, each layer having a plane high thermal conductivity along afirst axis and a lower thermal conductivity along a second axis.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting example components of an embodimentof a near-eye display (NED) device system.

FIG. 2A is a block diagram of example hardware components in a controlcircuitry embodiment of a NED device.

FIG. 2B is a top view of a near-eye display embodiment being coupledwith a projection light engine having an external exit pupil.

FIG. 3A is a perspective view and FIG. 3B is a top view of a secondexample of a head mounted display embodiment of a near-eye displaydevice system.

FIG. 4A is an example of a first thermal management solution including abonded graphite layer attached to a head mounted display.

FIG. 4B is a cross section along lines B-B in FIG. 4A.

FIG. 5A is an example of the first thermal management solution includinga bonded graphite layer attached to another embodiment of a head mounteddisplay.

FIG. 5B is a cross section along lines B-B in FIG. 5A.

FIG. 6A is a top view of a of a head mounted display embodiment of anear-eye display device system illustrating another thermal managementsolution including a multi-layer graphite stack.

FIG. 6B is a cross-section along line B-B in FIG. 6A.

FIG. 6C is an enlarged view of a multiple graphite layer stack.

FIG. 6D is a cross-section of another embodiment of a multi-layercopper/graphene stack.

FIG. 7A is a top view of a of a head mounted display embodiment of anear-eye display device system illustrating another thermal managementsolution including an encased graphite stack structure.

FIG. 7B is a cross-section along line B-B in FIG. 7A.

FIG. 7C is an enlarged view of a first embodiment of an encased multiplegraphite layer stack.

FIG. 7D is an enlarged view of a second embodiment of an encasedmultiple graphite layer stack.

FIG. 7E is a top view of a of a head mounted display embodiment of anear-eye display device system illustrating an encased graphite stackstructure mounted to the exterior of the system.

FIG. 7F is a cross-sectional view along line F-F in FIG. 7E.

FIG. 8 is a perspective view of the first embodiment of the head mounteddisplay device utilizing an embedded and encased graphite stack.

FIGS. 9 and 10A are top views illustrating another thermal managementsolution including a buttressed frame structure.

FIG. 10B is a cross-sectional view along line B-B in FIG. 10A

FIG. 11A is a side view of the thermal management solution of FIG. 9.

FIG. 11B is a cross-section along line B-B in FIG. 11A.

DETAILED DESCRIPTION

The technology provides techniques for thermal management in wearabledevices. utilizing a combination of techniques to remove heat from areasof active components in the device. In one embodiment, the device is ahead mounted display and a passive pseudo heat pipe structure isprovided. A passive pseudo-heat pipe structure used in a wearable deviceincludes a multilayer stack of graphite sheets, each sheet having aplane high thermal conductivity oriented along a first axis and a planeof lower thermal conductivity along a second axis different from thefirst axis. The stack has a three-dimensional shape including a lengthand a width where the length is longer than the width and the first axisaligns parallel to said length, the multilayer stack having a heightless than the width. A plurality of bonding layers interspersed betweeneach sheet of the multilayer stack, each bonding layer thermallycoupling each sheet to a respective adjacent sheet. The bonding layersmay comprise metal layers or adhesive layers. The pipe structure may beused in an optical mounting structure having heat producing controlcircuitry and temple arms adapted to secure the mounting structure tothe head of a wearer. In this embodiment, a bonded stack of graphitelayers is thermally bonded to at least the control circuitry and theoptical mounting structure, each layer having a plane high thermalconductivity along a first axis and a lower thermal conductivity along asecond axis.

The technology will be described with reference to a see-through headmounted display device, and the issues attending thermal management insuch a device. It will be recognized that the thermal managementtechniques described herein may be expanded to alternative wearabletechnology, as well as any devices where thermal management usingpassive heat transfer technology would be useful.

The technology will be described with reference to a see-through headmounted display device, and the issues attending thermal management insuch a device. It will be recognized that the thermal managementtechniques described herein may be expanded to alternative wearabletechnology, as well as any devices where thermal management usingpassive heat transfer technology would be useful.

Head-mounted displays, like other high powered computing devices producelarge amounts of heat that needs to be quickly and efficiently directedaway from the source and dissipated into the environment. This is usefulin wearable devices as the surface/skin temperature of the deviceaffects the usability and comfort of the user. There are a number ofeffective methods for transferring and dissipating heat currently usedin the electronics industry. Traditional methods for cooling highpowered electronics include passive cooling methods that are generallybulky and heavy and not particularly suitable for being used in wearabledevices. In addition, typical materials used in cases (e.g.polycarbonate, LCP) have very poor thermal properties and createinefficiencies in the thermal system as a whole. Improving even smallinefficiencies in the thermal system will allow for better deviceperformance and longevity over all.

FIG. 1 is a block diagram depicting example components of a waveguidedisplay implemented in a Near Eye Display (NED) system 8 including acompact projection light engine and diffractive waveguide. In theillustrated embodiment, a NED device system 8 includes a near-eyedisplay (NED) device in a head-mounted display (HMD) device 2 andcompanion processing module 4. HMD 2 is communicatively coupled tocompanion processing module 4. Wireless communication is illustrated inthis example, but communication via a wire between companion processingmodule 4 and HMD 2 may also be implemented. In an embodiment, HMD 2includes a NED device having a projection light engine 120 and near-eyedisplay 14 having a waveguide.

In this embodiment, HMD 2 is in the shape of eyeglasses having a frame115, with each display optical system 14 l and 14 r positioned at thefront of the HMD 2 to be seen through by each eye when worn by a user.Each display optical system 14 l and 14 r is also referred to as adisplay or near-eye display 14, and the two display optical systems 14 land 14 r together may also be referred to as a display or near-eyedisplay 14. In this embodiment, each display optical system 14 l and 14r uses a projection display in which image data (or image light) isprojected into a user's eye to generate a display of the image data sothat the image data appears to the user at a location in a threedimensional field of view (FOV) in front of the user.

In this embodiment, frame 115 provides a convenient eyeglass frameholding elements of the HMD 2 in place as well as a conduit forelectrical and thermal connections. In an embodiment, frame 115 providesa NED device support structure for a projection light engine 120 and anear-eye display 14 as described herein. Some other examples of NEDdevice support structures are a helmet, visor frame, goggles support orone or more straps. The frame 115 includes a nose bridge 104, an opticalsystem structure or housing 131 (including a left side housing 131 l andright side housing 131 r) joined by the nose bridge 104, a front topcover section 117, a respective projection light engine housing 130 foreach of a left side housing (1301) and a right side housing (130 r) ofHMD 2 as well as left and right temples or side arms 102 l and 102 rwhich are designed to rest on each of a user's ears. In this embodiment,nose bridge 104 includes a microphone 110 for recording sounds andtransmitting audio data to control circuitry 136. On the exterior of theside housing 1301 and 130 r are respective outward capture devices 1131and 113 r (such as cameras) which capture image data of the realenvironment in front of the user for mapping what is in a FOV of anear-eye display (NED) device. The frame components 115, 117, 104, 130,131 comprise an optical mounting structure for the display opticalsystems 14 and the sensors including microphone 110 and cameras 113.

In this embodiment, dashed lines 128 are illustrative examples of someelectrical connection paths which connect to control circuitry 136, alsoillustrated in dashed lines. One dashed electrical connection line islabeled 128 to avoid overcrowding the drawing. The electricalconnections and control circuitry 136 are in dashed lines to indicatethey are under the front top cover section 117 in this example. As notedin the drawings, the control circuitry and other electronic componentssuch as the displays are mounted to interior surfaces of the opticalmounting structure or housing. There may also be other electricalconnections (not shown) including extensions of a power bus in the sidearms for other components, some examples of which are sensor unitsincluding additional cameras, audio output devices like earphones orunits, and perhaps an additional processor and memory. Some examples ofconnectors 129 as screws are illustrated which may be used forconnecting the various parts of the frame together.

The companion processing module 4 may take various embodiments. In someembodiments, companion processing module 4 is in a portable form whichmay be worn on the user's body, e.g. a wrist, or be a separate portablecomputing system like a mobile device (e.g. smartphone, tablet, laptop).The companion processing module 4 may communicate using a wire orwirelessly (e.g., WiFi, BLUEOOTH® telecommunication services, infrared,an infrared personal area network, RFID transmission, wireless UniversalSerial Bus (WUSB), cellular, 3G, 4G or other wireless communicationmeans) over one or more communication network(s) 50 to one or morenetwork accessible computing system(s) 12, whether located nearby or ata remote location. In other embodiments, the functionality of thecompanion processing module 4 may be integrated in software and hardwarecomponents of HMD 2.

Image data is identified for display based on an application (e.g. agame or messaging application) executing on one or more processors incontrol circuitry 136, companion processing module 4 and/or networkaccessible computing system(s) 12 (or a combination thereof) to provideimage data to near-eye display 14.

FIG. 2A is a block diagram of example hardware components including acomputing system within control circuitry of a NED device. Controlcircuitry 136 provides various electronics that support the othercomponents of HMD 2. In this example, the control circuitry 136 for aHMD 2 comprises a processing unit 210, a memory 244 accessible to theprocessing unit 210 for storing processor readable instructions anddata. A network communication module 137 is communicatively coupled tothe processing unit 210 which can act as a network interface forconnecting HMD 2 to another computing system such as the companionprocessing module 4, a computing system of another NED device or onewhich is remotely accessible over the Internet. A power supply 239provides power for the components of the control circuitry 136 and theother components of the HMD 2 like the capture devices 113, themicrophone 110, other sensor units, and for power drawing components fordisplaying image data on near-eye display 14 such as light sources andelectronic circuitry associated with an image source like a microdisplayin a projection light engine.

The processing unit 210 may comprise one or more processors (or cores)such as a central processing unit (CPU) or core and a graphicsprocessing unit (GPU) or core. In embodiments without a separatecompanion processing module 4, processing unit 210 may contain at leastone GPU. Memory 244 is representative of the various types of memorywhich may be used by the system such as random access memory (RAM) forapplication use during execution, buffers for sensor data includingcaptured image data and display data, read only memory (ROM) or Flashmemory for instructions and system data, and other types of nonvolatilememory for storing applications and user profile data, for example. FIG.2A illustrates an electrical connection of a data bus 270 that connectssensor units 257, display driver 246, processing unit 210, memory 244,and network communication module 137. Data bus 270 also derives powerfrom power supply 239 through a power bus 272 to which all theillustrated elements of the control circuitry are connected for drawingpower.

Control circuitry 136 further comprises a display driver 246 forselecting digital control data (e.g. control bits) to represent imagedata that may be decoded by microdisplay circuitry 259 and differentactive component drivers of a projection light engine (e.g. 120 in FIG.2B). A microdisplay, such as microdisplay 230 shown in FIG. 3C, may bean active transmissive, emissive or reflective device. For example, amicrodisplay may be a liquid crystal on silicon (LCoS) device requiringpower or a micromechanical machine (MEMs) based device requiring powerto move individual mirrors. An example of an active component driver isa display illumination driver 247 which converts digital control data toanalog signals for driving an illumination unit 222 which includes oneor more light sources, such as one or more lasers or light emittingdiodes (LEDs). In some embodiments, a display unit may include one ormore active gratings 253, such as for a waveguide, for coupling theimage light at the exit pupil from the projection light engine. Anoptional active grating(s) controller 249 converts digital control datainto signals for changing the properties of one or more optional activegrating(s) 253. Similarly, one or more polarizers of a projection lightengine may be active polarizer(s) 255 which may be driven by an optionalactive polarizer(s) controller 251. The control circuitry 136 mayinclude other control units not illustrated here but related to otherfunctions of a HMD 2 such as providing audio output, identifying headorientation and location information.

FIG. 2B is a top view of an embodiment of a near-eye display 14 l beingcoupled with a projection light engine 120 having an external exit pupil121. In order to show the components of the display optical system 14,in this case 14 l for the left eye, a portion of the top frame cover 117covering the near-eye display 14 l and the projection light engine 120is not depicted. Arrow 142 represents an optical axis of the near-eyedisplay 14 l.

In this embodiment, the near-eye displays 14 l and 14 r are opticalsee-through displays. In other embodiments, they can be video-seedisplays. Each display includes a display unit 112 illustrated betweentwo optional see-through lenses 116 and 118 and including a waveguide123. The optional lenses 116 and 118 are protective coverings for thedisplay unit. One or both of them may also be used to implement a user'seyeglass prescription. In this example, eye space 140 approximates alocation of a user's eye when HMD 2 is worn. The waveguide directs imagedata in the form of image light from a projection light engine 120towards a user's eye space 140 while also allowing light from the realworld to pass through towards a user's eye space, thereby allowing auser to have an actual direct view of the space in front of HMD 2 inaddition to seeing an image of a virtual feature from the projectionlight engine 120.

In some embodiments, a waveguide 123 may be a diffractive waveguide.Additionally, in some examples, a waveguide 123 is a surface reliefgrating (SRG) waveguide. An input diffraction grating 119 couples animage light from a projection light engine 120. Additionally, awaveguide has a number of exit gratings 125 for an image light to exitthe waveguide in the direction of a user's eye space 140. One exitgrating 125 is labeled to avoid overcrowding the drawing. In thisexample, an outermost input diffraction grating 119 is wide enough andpositioned to capture light exiting a projection light engine 120 beforethe light exiting the projection light engine has reached its exit pupil121. The optically coupled image light forms its exit pupil in thisexample at a central portion of the waveguide.

FIG. 2B shows half of a HMD 2. For the illustrated embodiment, a fullHMD 2 may include another display optical system 14 with another set ofoptional see-through lenses 116 and 118, another waveguide 123, as wellas another projection light engine 120, and another of outward facingcapture devices 113. In some embodiments, there may be a continuousdisplay viewed by both eyes, rather than a display optical system foreach eye. In some embodiments, a single projection light engine 120 maybe optically coupled to a continuous display viewed by both eyes or beoptically coupled to separate displays for the eyes. Additional detailsof a head mounted personal A/V apparatus are illustrated in U.S. patentapplication Ser. No. 12/905,952 entitled Fusing Virtual Content IntoReal Content, Filed Oct. 15, 2010 now issued as U.S. Pat. No. 8,884,984.

FIGS. 3A and 3B an alternative embodiment of the HMD layout and framestructure. Like numerals for the embodiment the representations of FIGS.3A and 3B represent like parts to those parts illustrated in theembodiment of FIGS. 1-2. FIG. 3A is a perspective view and FIG. 3B a topview of an HMD 2 a.

In the embodiment of FIGS. 3A and 3B, frame 115 may by generallyreferred to as a wraparound-type frame, where the display opticalsystems 14 are integrated or mounted into a polymer, plastic orcomposite frame material comprising elements 110, 131, 102. The templeor side arms 102 may be created to wrap around the head of a wearer andrest on the wearer's ears. In one embodiment, the temples are created bya forward component 102 r 1 and 102 l 1 and a rear component 102 r 2 and102 l 2. A mechanical adjustment 133 r, 1331 may be provide between theforward and rear portions of temples 102. In an alternative embodiment,the temples or side arms 102 may be continuous. Control circuitry 136 islocated to be in a similar position in the embodiment of FIGS. 3 and 4with respect to the embodiment of FIGS. 1 and 2.

Those skilled in the art will readily understand that electroniccomponents and circuitry utilized in the systems 2 and 2 a operate moreefficiently when cooling takes place between the circuits and theambient environment. In a system 2 and 2 a, cooling components may raiseambient temperatures of the structural components to a temperaturehigher than the ambient but insufficient for a wearer to notice. Forexample, an exemplary temperature range imperceptible to a human wearerwould be less than 50 deg. F.

In order to provide passive heat dissipation, various techniques andcombinations thereof may be utilized.

Nanocarbon Infused Frame Elements

In one embodiment, carbon nanoparticles are mixed with the framematerial to provide efficient passive heat transfer within the deviceframe 115 including frame components 102, 130 131, 110, and 115. Thecarbon nanoparticles increase the thermal conduction properties of theframe elements and provide a lightweight way of increasing the thermalconduction of a base material such as a polymer used to create theframe. A number of heat emitting electrical components, such as thecontrol circuitry and power supplies discussed above, are included inthe device. The techniques discussed herein provide various means forremoving heat from the heat emitting electrical components in a wearabledevice.

Carbon nanoparticles, nanodots or nanopowder may comprise spherical highsurface area graphitic carbon. Carbon nanoparticles may comprisegraphene, and in particular single layer graphene (SLG), bilayergraphene (BLG), few layer graphene (FLG), multilayer graphene (MLG)carbon nanotubes, pyrolytic graphite flakes or any other nanocarbongeometries. Carbon nanoparticles may range in size from 10-100nanometers (nm) in diameter with a specific surface area in the 2-50m2/g. Carbon nano-particles are available in passivated and high purity,and coated and dispersed forms.

Frames such as those illustrated in FIGS. 1-3B may be formed of moldedpolymers from any of a number of thermoplastic polymers, including, forexample acrylonitrile butadiene styrene plastic (Acrylonitrile ButadieneStyrene, ABS), which has a high degree of rigidity and plasticitycharacteristics. Plastic is plasticized styrene (Polymerising Styrene),propylene (Acrylonitrile) and polybutadiene (Polybutadiene) mixed intobutadiene rubber (Latex). The base material may have added thereto andamount of 2-10% loading by volume of carbon nanoparticles, nanopowder,pyrolytic graphite flakes or carbon nanotubes. Adding the carbonmaterial to the material matrix prior to formation process forcomponents 102, 130, 131 improves the thermal conductivity of each ofthe components. In the process, the carbon nanoparticles can be addedsimultaneously additives such as stabilizers, lubricants and coloringmaterials. It will be appreciated that any suitable polymer materialwhich may be formed into a desired shape and which when cooled providesa suitable rigidity to ensure stability for the optical platform(display systems 14) under various wearable conditions can be used. Thepercentage by concentration of the carbon nanoparticles may be in arange of 2 to 10% and in a range of 2-4% loading by volume.

The nanocarbon infused structural components may be used in conjunctionwith any of the later described thermal management techniques describedherein.

Formation of frame parts in accordance with a method of the presenttechnology includes the use of injection molding and extrusion moldingtechniques to form the molded parts for the frame 115. In order tocreate a part such as temple 102 r or 102 r 1, an injection moldingprocess includes steps of: (1) providing an injection molding apparatus;(2) mixing the base polymer pellets or powder comprising the framematerial and carbon microparticles uniformly; (3) obtaining the mixturefrom step (2) and adding the mixture to the injection molding apparatusincluding a heating cylinder; (4) melting the mixture at hightemperature to create a molten mixture; (5) injecting the molten mixturethrough an injection nozzle into a closed mold cavity; (6) and coolingthe molten mixture in a mold to solidify the desired component. Anextrusion process includes (1) providing a extrusion molding device; (2)mixing the engineering polymer pellets or powder comprising the framematerial and carbon nanosphere particles uniformly; (3) obtaining themixture; (4) melting the mixture at high temperature; and (4) forming amolten mixture through a die; and cooling the molten mixture in a moldto solidify the desired part.

In accordance with the present technology, at least temples 102 r 1 and102 l may be formed of nanocarbon infused materials. In a furtherembodiment with respect to HMD 2 a, at least elements 102 r 1 and 102 l1 are formed of nanocarbon infused materials. It will be readilyunderstood that any of the components 102, 117, 130, 131 may be formedof nanocarbon infused materials. In a further embodiment, elements 102 r2 and 102 l 2 are formed of nanocarbon infused materials.

In alternative embodiments, the carbon nanoparticles may comprisepyrolytic graphite flakes or carbon nanotubes. In any embodiment, theframe may comprise a polycarbonate with a 2%-4% loading by volume ofmono-layer graphene flakes with a very large aspect ratio to replaceglass-filled polycarbonate. The current material is being used for itsrobustness, strength and ability to be injection molded. The graphenedoped polymer possesses all the same increased properties mechanically,but also boasts a high increase in thermal properties. The increasedthermal conductivity of the doped polymer will allow for better heatspreading on the surface on the device, resulting in lower touchtemperatures as well as more efficient thermal dissipation from theelectronics and display.

Graphene doped polymers, unlike other filled polymers, also createelectrically conductivity. As such, the amount of graphene and type(shape-factor, size of flakes, number of atomic layers, aspect ratio,etc.) can be custom tailored to meet the needs of the product andsub-assemblies with respect to EMI shielding.

Bonded Graphite Layer

A further embodiment of the present technology utilizes graphite orgraphene thermal pseudo-heat pipe to remove heat from the activecircuitry 136. FIGS. 4A-5B represent an embodiment of a wearable deviceutilizing the present technology.

Graphites possess anisotropic structures and thus exhibit or possessmany properties that are highly directional e.g. thermal and electricalconductivity and diffusion. Graphites are made up of layer planes ofhexagonal arrays or networks of carbon atoms. These layer planes ofhexagonally arranged carbon atoms are substantially flat and areoriented or ordered so as to be substantially parallel and equidistantto one another. The substantially flat, parallel equidistant sheets orlayers of carbon atoms, usually referred to as graphene layers or basalplanes, are linked or bonded together and groups thereof are arranged incrystallites. As used herein, the term “graphene” or “graphene film”denotes the atom-thick carbon sheets or layers that stacks up to formcleavable layers (or mica-like cleavings) in graphite.

Graphite may be made up of a plurality layers or planes. A heat sinkdesign can be a complex task requiring extensive math—finite elementanalysis, fluid dynamics, etc. In designing heat sinks, various factorsare taken into consideration, including thermal resistance, area of theheat sink, and the shape of the heat sink.

Some types of graphite, such as pyrolytic graphite, are available in asheet form, which has a high thermal conductivity in the plane of thesheet and a lower thermal conductivity perpendicular to the plane of thesheet. In one form, the pyrolytic graphite is oriented such that thehigh-conductivity plane lies parallel to the direction of heat transfer(away from the active circuitry 136 and toward the ends of temples 102.

In one embodiment, a graphite layer contacts at least a portion of theactive circuitry 136 and is routed to an exterior portion of the frame115. As used herein, the term “graphite layer” refers to at least onegraphene layer. A graphite layer may in some embodiments comprise asheet of pyrolytic graphite.

FIG. 4A illustrates an attached graphite layer 402 (comprising a leftside layer 4021 and right side layer 402 r) provided on the HMD 2 in theembodiment of FIG. 1. FIG. 4B is a cross-section of the graphite layer402 applied to the temples 102 of the frame 115. It will be understoodthat a thermal coupling of graphite or another thermally conductivematerial may be routed from the circuitry 136 to the graphite layer 402.As seen in the cross-section of FIG. 4B, the layer may be applied to theside of the temples 102 and/or to the top of the temple. Otherconfigurations of the graphite layer 402 will be understood to be withinthe scope of the present technology, including providing the layer 402on three sides of the frame and providing the layer 402 on all foursides of the frame. The technology is not limited to the shape of theframe, nor the particular nature of the wearable device.

FIG. 5A illustrates an attached graphite layer 404 utilized in the HMD2A. As illustrated therein, graphite layer 404 (comprising a left sidelayer 404 l and right side layer 404 r) are attached to temples 102 (andin particular portions 102 l 1 and 102 r 1, respectively). A portion 404r′ and 404 l′ of each graphite layer engages circuitry 136, with thelayer attached to the exterior of the temples 102 l 1 and 102 r 1. Asillustrated in FIG. 5b , the graphite layer 404 is secured to theexterior wall of each temple (in this view, temple 102 r 1).

In one embodiment, the graphite layer may comprise pyrolytic graphite.Pyrolytic graphite is a form of graphite manufactured by using a rawmaterial of a highly crystalline polymer. The polymer is put through apyrolysis process devoid of oxygen. Not having oxygen keeps combustionfrom occurring and instead all the volatiles present in the polymerchains are released and resulting in a base structure of carbon rings.High temperature and pressure annealing then occurs to wedge thosepolymer backbones of carbon into a layered sheet structure viable forhigh thermal conductivity. The material is grown onto a substrate givingit a layered composition and may have different properties in differentplanes. Commercially available pyrolytic graphite is available inconductivities ranging from 700 W/mk to 2000 W/mK and in sheetthicknesses ranging from 10-150 μm.

It should be understood that “pyrolythic graphite” may include “thermalpyrolytic graphite” as well as “highly oriented pyrolytic graphite”, and“compression annealed pyrolytic graphite,” referring to graphitematerials consisting of crystallites of considerable size, thecrystallites being highly aligned or oriented with respect to each otherand having well ordered carbon layers or a high degree of preferredcrystallite orientation, with an in-plane (a-b direction) thermalconductivity greater than 1,000 W/m-K. In one embodiment, the TPG has anin-plane thermal conductivity greater than 1,500 W/m-K

The graphite layer may be selected from any material having a highthermal conductivity including pyrolytic graphite, thermal pyrolyticgraphite, compression annealed pyrolytic graphite, thermal pyrolyticgraphite, highly ordered pyrolytic graphite, pyrolytic graphite, and thelike.

In one embodiment, the graphite layer is attached to the temples 102using a suitable adhesive material. In one embodiment, it is desirableto attach the graphite under constraints which would not adverselyaffect the sensitive components of the electronics or sensors, nor themechanical stability of the frame. Because the components (such ascameras 113 and microphone 110 may be sensitive to misalignment if frame115 becomes mechanically distorted, post-processing of the frame 115 toapply the graphite layer may adversely affect the performance of thedevice 2/2 a.

Graphite layers 402, 404 may be secured to HMDs 2/2A using any suitableform of adhesive to bond the graphite layer to the material comprisingthe frame elements. Suitable adhesive materials include, for example,inorganic and organic adhesives. An exemplary adhesive material is anepoxy. In one embodiment, the bonding material exhibits thermalconductivity properties, e.g., a thermally conductive epoxy. Acrylicadhesives may also be utilized.

Suitable graphite layers include pyrolytic graphite sheets availablefrom Panasonic Corporation. Such sheets may include applications with orwithout acrylic adhesives and adhesive tapes.

In one embodiment, the graphite layer may be preformed into a shapesuitable for application to the frame elements and which may bethermally connected to the control circuitry 136 or other electroniccomponents of an HMD.

In another alternative, graphene may be grown or laminated on one ormore surfaces of the frame. Graphene may be applied by any of a numberof methods, including by chemical vapor deposition (CVD), SiC thermaldecomposition, or a graphene oxide reduction. In a CVD method, a filmcomprising graphene is formed on one surface of a substrate (which maycomprise a portion of the frame) the graphene film tailored for theparticular use by the process chosen.

Nanocarbon Infused Frame with Graphite Layer

A further embodiment of the present technology includes the use ofnanocarbon infused frame elements with an applied graphite layer.

The combination of the graphite layer in conjunction with the nanocarboninfused material increases the thermal conduction properties of theframe 115. It will be readily understood that any of the components 102,117, 130, 131 may be formed of nanocarbon infused materials.

In accordance with the present technology, at least temples 102 r and102 l may be formed of nanocarbon infused materials and have appliedthereto a graphite layer in accordance with the foregoing embodimentswherein the graphite layer bonds to a surface of the temple 102 l 1 and102 r 1. In a further embodiment, elements 102R2 and 102L2 are formed ofnanocarbon infused materials.

Graphite layers 402, 404 may be secured each other using any suitableform of adhesive to bond the graphite layers to each other, and thestack to the material comprising the frame elements. Suitable adhesivematerials include, for example, the inorganic and organic adhesivesprovided above including epoxy. In one embodiment, the bonding materialexhibits thermal conductivity properties, e.g., a thermally conductiveepoxy. Acrylic adhesives may also be utilized. Suitable graphite layersinclude any of the pyrolytic graphite materials discussed herein and mayinclude pyrolytic graphite sheets available from Panasonic Corporation.Such sheets may include applications with or without acrylic adhesivesand adhesive tapes. In one embodiment, the adhesives used are curable atambient temperatures in a range of 60-80 degrees Fahrenheit.

It will be understood that the application of a graphite layer incombination with the nanocarbon infused frame elements may further beenhanced by use of any of the below thermally conductive graphitestructures described herein.

In order to create a part such as temple 102 r or 102 r 1, use of theinjection molding and/or extrusion process discussed above may beutilized. Following the aforementioned cooling steps, the graphite layermay be applied to the desired location of the part by (1) forming thegraphite layer into a suitable shape for application to the partsurface, (2) applying one of the aforementioned adhesives to the frameelement in a contact region; (3) applying the graphite layer and (4)applying a uniform pressure to the graphite layer to allow curing of theadhesive to secure the layer to the part.

Graphite Layer Stack

A further embodiment of the present technology includes the use amulti-layer stack of graphite layers constructed to be applied to thesurface of the elements. Construction of a multi-layer stack of graphitesheets may provide a thermal highway which can be attached to componentsof the HMD 2/2 a.

FIGS. 6A-6C illustrates use of the multilayer stack in conjunction withthe graphite layer thermally coupled to the active circuitry 136. FIG.6A illustrates one configuration of the multiple graphite layer stack inaccordance with the technology applied to frame elements of an HMDdevice and thermally coupled to active circuits in HMD 2 a. In FIG. 6A,two stacks 600 r and 600 l are illustrated

A representation of a multilayer stack of graphite layers is illustratedin FIG. 6C. In FIG. 6C, individual graphite layers 602-608 are securedto and sandwich adhesive layers 612-616. While four graphite layers areillustrated, any number of graphite and adhesive layers may be utilizedto make stack 600.

One difficulty in assembling stack 602 is that graphite layers by naturenot wish to adhere to each other. In addition, granites may be tearsensitive, and the structure can be brittle when applied to the exteriorof a frame which can be exposed to ambient conditions. Suitable adhesivematerials include, for example, inorganic and organic adhesives. Anexemplary adhesive material is an epoxy. In one embodiment, the bondingmaterial exhibits thermal conductivity properties, e.g., a thermallyconductive epoxy. Acrylic adhesives may also be utilized. Suitablegraphite layers include any of the pyrolytic graphite materialsdiscussed herein. The graphite stack 602 can be formed into any of anumber of three-dimensional shapes by configuring the graphite layersassembled into the stack.

In one embodiment, a stack 600 is not coupled by portions 404 r′ and 404l′ to the active circuitry 136, but is attached to any one or more ofthe surfaces of the frame components such as temples 102, cover section117, and housing 131.

It will be understood that the application of a graphite layer stack maybe utilized in combination with the nanocarbon infused frame elementsdiscussed above.

In order to create a part such as temple 102 l 1 or 102 r 1, use of theinjection molding and/or extrusion process discussed above may beutilized. Prior to formation of the part or thereafter, a multi-layerstack is created by creating the multilayer stack 600 including (1)forming the graphite layers into a suitable shape to be applied to thesurface of a frame element; (2) applying adhesive to a first of thegraphite layers followed by (3) applying a second graphite layer on theadhesive; (4) applying uniform pressure to the graphite layer; and(optionally) (5) repeating steps (1)-(3) for any number of additionallayers. Alternatively, steps (1)-(3) may be repeated for any number oflayers prior to applying uniform pressure to the outermost layer in thestack. Thereafter, the stack 600 is applied to a frame part using any ofthe aforementioned adhesives discussed herein. The part may be createdwith any of the materials discussed herein and any of the aforementionedpart fabrication processes, with or without infused nanocarbon in thepart material.

A thermal coupling structure of graphite (such as region 404 r′) may beincorporated during stack formation or glued to the stack 600thereafter.

Although the graphite layer is illustrated in a particular configurationin FIGS. 6A-6C, the layers may be provided in any of a number of regionson the device. Any surface of the temples 102 may include a graphitelayer (whether coupled to a thermal coupling or attached to the deviceto promote heat transfer away from any active components).

In some embodiments, the resulting structure is a flexible structurethat can be molded to a surface of the frame, as illustrated, or used inany of a number of applications. The flexibility of the structure andthe thermal performance of the structure depends on the bonding layersbetween the graphite layers.

An alternative embodiment of a graphite layer structure may be formed asa copper-graphene structure 650. In this embodiment, a central, planersheet of copper 656 having a thickness ranging from 20-50 nm is coatedon both sides with layers of graphene 654, 658 after which copper layers652, 660 are applied to respective graphene layers 654, 658. Thegraphene may be formed by any of the aforementioned processes and layers652 and 660 of copper may be deposited by a suitable vapor or physicaldeposition process.

Encased Graphite Layer Stack

A further embodiment of the present technology includes the use amulti-layer stack of graphite layers constructed within a metallicenclosure which may be thermally connected to active circuitry andthereafter applied to the surface of frame elements to act as a passivepseudo-heat pipe.

FIGS. 7-8 illustrate a multilayer stack of graphite constructed in anenclosed metallic casing. In one embodiment illustrated in FIG. 7D, anencased assembly 750 including the graphite stack 700 a may have astructure similar to graphite stack 600 illustrated above. Thisembodiment, plurality layers 702 through 708 are joined by adhesives712-716 after which the stack 700 a is encased in a metallic layer orcoating. FIG. 7C illustrates an alternative embodiment of an encasedassembly 750 including stack 700 b wherein no adhesive is used betweenthe multiple graphite layers. In the embodiment of FIG. 7C, directcontact between the layers 702-708 and the casing material ensuresthermal conduction.

The embodiment of FIG. 7D may be created by: (1) forming a firstgraphite layer into a suitable shape to be applied to the surface of aframe element; (2) applying adhesive to a first of the graphite layersfollowed by (3) applying a second graphite layer on the adhesive; (4)applying uniform pressure to the graphite layer; and (optionally) (5)repeating steps (1)-(3) for any number of additional layers.Alternatively, steps (1)-(3) may be repeated for any number of layersprior to applying uniform pressure to the outermost layer in the stack.After creation of stack 700 a, the stack is encased in a metallic casing715. The casing 715 is preferably made of a high conductivity metal suchas titanium, copper, tin, nickel, silver, aluminum, TiW (90/10, andother alloys), copper tin alloys, and alloys of the above metals). Thecasing extends around and encloses the pyrolytic graphite stack so thatthe pyrolytic graphite stack is embedded within the casing. In oneembodiment, the casing is hermetic, so that no external agents canpenetrate to contact the stack. The casing may be applied by metallicdeposition techniques or formed by mechanically manipulating workableforms of the aforementioned metals to encase the stack 700 a.

The embodiment of FIG. 7C may be created by: (1) forming a selectednumber of the graphite layers to be formed into the stack into asuitable shape to be applied to the frame element; (2) providing thegraphite layers and the coating material in a vacuum environment; (3)stacking successive graphite layers into a stack 700 b; (4) applyinguniform pressure to the graphite layers; and encasing the graphitelayers in the stack using one of (a) metallic deposition onto the stackor (b) mechanical manipulation of metal plates of sufficient size tosurround the stack followed by sealing the casing about the stack 700 b.

Suitable graphite layers include any of the pyrolytic graphite materialsdiscussed herein. The graphite material used in the stack should haveits high plane of conductivity arranged and oriented perpendicular tothe plane of the drawings of FIGS. 7C and 7D so that when arranged inthe device 2, high-conductivity plane lies parallel to the direction ofheat transfer (away from the active circuitry 136 and toward the ends oftemples 102).

FIG. 7A is a top view of the HMD device to a illustrating that theencased graphite layer stack structure can be incorporated into theframe materials of the device. Corporation the frame materials is alsoillustrated with respect to device two in FIG. 8. In this embodiment,the case stack, illustrated in Figures of be, is molded into the frameitself. FIGS. 7E and 7F illustrate positioning of the encased structureon a top portion of the device 2 a.

Various configurations of the encased graphite layer stack structure canbe utilized in accordance with the teachings of this technology. Thestructure may have various different three-dimensional forms, analternative components of the forms may be joined together. Asillustrated in FIG. 7D, two such structures may be formed in a linearmanner and joined together using any of the aforementioned techniques ofadhesive, creating the structures from native graphite sheets, or thelike.

With respect to FIGS. 7A and 7C, each encased structure may have alength L, width W and height H defined in accordance with the thermalmanagement objectives of the system. Each of the respective sheets ofgraphite in the layer stack may be defined and selected to have a planehigh thermal conductivity along a first axis and a plane of lowerthermal conductivity along a second axis. In one embodiment the plane isselected so that the axis of high conductivity aligns with the lengthand is parallel to an axis bisecting the length of the encased stack. Asnoted in FIG. 7A, the length is multiple times longer than the width theheight less than the width.

FIGS. 7E and 7F illustrate the encased structure 752 positioned on anexterior surface of an HMD 2 a. In the illustration of FIGS. 7E and 7F,the encased structure 752 is positioned on a top surface 910 of arm 102r 1. It should be understood that the structure 752 may be provided on abottom surface 912 or a side surface 914 of the arm. In addition, FIG.7E illustrates two encased structures 752 joined at an interface 753.Due to the workability of the metal encasing the structure 752, joiningof respective structures may occur by thermal bonding such asmechanically connecting, soldering or welding the respective structures752, or by forming the underlying graphite layers in to an angledstructure and thereafter encasing the formed angled structure in a metalcoating.

It will be understood that the application of a graphite layer stack maybe utilized in combination with the nanocarbon infused frame elementsdiscussed above. In addition, the encased structure may be utilized withthe stack 600 described above, alone or in combination therewith.

Buttressed Frame Structure

FIGS. 9-11 illustrate an alternative frame structure suitable for usewith any of the aforementioned devices 2 and 2 a. Although the subjectmatter will be illustrated with respect to the HMD 2 a, it will berecognized that similar techniques can be used with any type of framingstructure.

In FIGS. 9-11B, temples 102R1 and 102L1 have been formed to includevoids 900, 902, thereby creating arches adjacent the joining points ofthe temples 102 r 1 and 101L1 to temples 102R2 and 102L2, respectively,and housing 131. The voids effectively provide a arched temple structurewhich couples the housing 131 two other portions of the side arms102L2/102 r 2. Voids 900, 902 provide an increase in the surface areaavailable for convective and radiant heat transmission to the ambientenvironment. Any heat provided and transferred from the active circuitryto the temples 102 R1 and 102 l 1 can be more easily cooled by theambient environment. In the illustrated embodiment, void 900 includes afirst sidewall 912, second sidewall 914 and two arches 916, 918 joiningthe respective sidewalls

In addition, the voids 900, 902 increase the strength of the temples 102by using arch construction techniques. An arch is a pure compressionform resolving forces into compressive stresses and, in turn eliminatingtensile stresses. Given the architecture of HMDs 2/2 a, with forwardcomponents carrying most of the weight and support components (such asthe temples 102) stabilizing the device, strength in the templecomponents in combination with lightweight constructions is desirable.

Although the voids are illustrated as being provided only in elements102 r 1 and 102 l 1, it will be understood that the voids may be formedin temple portions 102R2 and 102L2, or in a unitary temple structuresuch as that provided in the HMD device 2.

In addition, the void architecture of FIGS. 9 and 10A can be utilizedwith any of the aforementioned thermal management techniques describedabove.

In particular, the components of the device of FIG. 9 may bemanufactured of nanocarbon infused materials as described above. Any oneor more of the graphite structures discussed above may be attached onthe surface of or embedded in the structures of FIG. 9.

FIG. 10A illustrates an example of using a graphite layers to thatdescribed above in FIG. 5A in combination with the voids 900, 902. Asillustrated therein, a graphite layer 404 is provided as in FIG. 5A withportions 404 r and 404 l being attached to elements 102 r 1 and 102 l 1having voids therein. Graphite layers 404 r and 404 l may be a sheet ofpyrolytic graphite, any of the graphite stacks illustrated herein, or alaminated layer of graphene.

FIG. 10B illustrates a cross-section along line B-B in FIG. 10A, showingthe top surface 910, bottom surface 912, first side 914 and second side916 of arm portion 102 r 1. In addition, the interior walls 918 and 912are illustrated. It will further be appreciated that graphite layer orlayers may be applied to the interior walls 918, 920 of the structure ofFIG. 10A. In FIG. 10B, only void 900 is illustrated, but it should beunderstood that structure 752 can be provided on both arms 102L and 102r

FIGS. 11A and 11B illustrate the use of the graphite layer structure 650described above wherein the structure 650 is encased in the frame 2 a.The structure 650 is thermally coupled to the heat producing componentsand extends into the void regions 900, 902 (In FIGS. 11A and 11B, onlyvoid 902 is illustrated, but it should be understood that structure 650can be provided on both arms 102 l and 102 r.)

In addition, the voids formed in components of the frame may takevarious shapes. The arcuate voids 900, 902 provide convection verticallywhen the device is worn by a wearer. This can provide convection withcooler air passing through and around the voids and frame element as itrises. However, the voids may be provided horizontally with respect todirection of the temples 102. Moreover, the voids may be provided in anynumber and shape. For example, a plurality of circular or other shapedbores may be provided in the frame elements

Additional graphite layers may be provided on the interior surfaces ofvoids 900, 902 or the outer surfaces of the temples 102.

Any one or more of the graphite layers, graphite stacks or encasedstructures may be embedded in the frame by manufacturing the framecomponents around the thermal structures. An injection molding processembedding such structures includes steps of: (1) providing an injectionmolding apparatus; (2) mixing the engineering polymer pellets or powdercomprising the frame material and carbon nanosphere particles uniformly;(3) obtaining the mixture from step (2) and adding the mixture to theinjection molding apparatus including a heating cylinder; (4) meltingthe mixture at high temperature; (5) providing the graphite layer,multilayer stack or encased graphite layer stack into a mold cavity andclosing the cavity; (6) injecting the molten mixture through aninjection nozzle into a closed mold cavity; and (7) cooling the moltenmixture in a mold to solidify the desired part. An extrusion processincludes (1) providing a extrusion molding device; (2) mixing theengineering polymer pellets or powder comprising the frame material andcarbon nanosphere particles uniformly; (3) obtaining the mixture; (4)melting the mixture at high temperature; (4) forming a molten mixturethrough a die to surround a graphite layer, multilayer stack or encasedgraphite layer stack; and (5) cooling the molten mixture in a mold tosolidify the desired part.

Aspects of Certain Embodiments

Embodiments of the technology include a multilayer stack of graphitesheets, each sheet having a plane high thermal conductivity orientedalong a first axis and a plane of lower thermal conductivity along asecond axis different from the first axis, the stack having athree-dimensional shape including a length and a width where the lengthis longer than the width and the first axis aligns parallel to saidlength, the multilayer stack having a height less than the width; and aplurality of bonding layers interspersed between each sheet of themultilayer stack, each bonding layer thermally coupling each sheet to arespective adjacent sheet.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the stack is comprised of a pluralityof sheets of pyrolytic graphite.

Embodiments of the technology may further include any of theaforementioned embodiments wherein an outer layer of the stack is bondedto a structure, the structure including heat producing componentsprovided in a frame, the stack thermally coupled to at least one of theheat producing components.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the frame includes an arm extendingin a direction away from the heat producing components, and themultilayer stack is bonded to the arm.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the multilayer stack is embedded in amaterial formed into the frame.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the length is defined by a first endand a second end, the first end coupled to the heat producingcomponents, the second end extending away from the heat producingcomponents and bonded to an exterior surface of the structure.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using a metal.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using anadhesive.

Embodiments of the technology may further include any of theaforementioned embodiments implemented in a wearable device includingelectronic components. Such embodiments may include a mounting structureincluding the electronic components; and a stack of graphite layers andthermally coupled to the electronic components, each layer having aplane of high thermal conductivity oriented along a first axis and alower thermal conductivity oriented along a second axis, the stackhaving a three-dimensional shape including a length and a width wherethe length is longer than the width and the first axis is parallel tosaid length, the stack having a height less than the width, an outerlayer of the stack bonded to an exterior surface of the mountingstructure such the length extends away from the electronic components.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the stack is comprised of a pluralityof sheets of pyrolytic graphite.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the structure includes an armextending in a direction away from the electronic components, and thestack is bonded to the arm.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using a metal.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using anadhesive.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the mounting structure is comprisedof a material including a plurality of carbon nanoparticles.

Embodiments of the technology may further include any of theaforementioned embodiments in a head mounted display including heatproducing electrical components operating a display optical system. Suchembodiments include: an optical mounting structure including the heatproducing electrical components, the mounting structure housing thedisplay optical system coupled to the heat producing electricalcomponents, and first and second temple arms extending away from theheat producing electrical components and the display optical systems,the temple arms adapted to secure the mounting structure to the head ofa wearer; and a bonded stack of graphite layers, the stack thermallybonded to at least the heat producing electrical components and theoptical mounting structure, each layer having a plane high thermalconductivity along a first axis and a lower thermal conductivity along asecond axis, the stack having a three-dimensional shape including alength and a width where the length is longer than the width and thefirst axis aligns parallel to said length, the stack having a heightless than the width.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the stack is comprised of a pluralityof sheets of pyrolytic graphite.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the bonded stack is embedded in amaterial formed into the structure.

Embodiments of the technology may further include any of theaforementioned embodiments wherein the length is defined by a first endand a second end, the first end coupled to the heat producingcomponents, the second end extending away from the heat producingcomponents and bonded to an exterior surface of the structure.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using a metal.

Embodiments of the technology may further include any of theaforementioned embodiments wherein stack comprises a plurality ofgraphite sheets, each sheet bonded to a respective sheet using anadhesive.

Although the subject matter has been described in language specific tostructural features and/or acts, it is to be understood that the subjectmatter defined in the appended claims is not necessarily limited to thespecific features or acts described above. Rather, the specific featuresand acts described above are disclosed as examples of implementing theclaims and other equivalent features and acts that would be recognizedby one skilled in the art are intended to be within the scope of theclaims.

What is claimed is:
 1. An apparatus comprising: a wearable device,including: electronic components; a mounting structure including theelectronic components; and a stack of graphite layers thermally coupledto the electronic components, each of the layers having a plane of highthermal conductivity oriented along a first axis and a lower thermalconductivity oriented along a second axis, the stack having athree-dimensional shape including a length and a width where the lengthis longer than the width and the first axis is parallel to said length,the stack having a height less than the width, an outer layer of thestack of graphite layers bounded to an exterior surface of the mountingstructure such that the length extends away from the electroniccomponents.
 2. The apparatus of claim 1 wherein the stack of graphitelayers is comprised of a plurality of sheets of pyrolytic graphite. 3.The apparatus of claim 2 wherein the mounting structure includes an armextending in a direction away from the electronic components, and thestack is bonded to the arm.
 4. The apparatus of claim 3 wherein thestack of graphite layers comprises a plurality of graphite sheets and aplurality of bonding layers interspersed between the graphite sheets,each one of the bonding layers comprising a metal.
 5. The apparatus ofclaim 3 wherein the stack of graphite layers comprises a plurality ofgraphite sheets and a plurality of bonding layers interspersed betweenthe graphite sheets, each one of the bonding layers comprising anadhesive.
 6. The apparatus of claim 3 wherein the mounting structure iscomprised of a material including a plurality of carbon nanoparticles.7. A head mounted display including heat producing electrical componentsoperating a display optical system, comprising: an optical mountingstructure including the heat producing electrical components, theoptical mounting structure housing the display optical system coupled tothe heat producing electrical components, and first and second templearms extending away from the heat producing electrical components andthe display optical system, the temple arms adapted to secure theoptical mounting structure to a head of a wearer; and a bonded stack ofgraphite layers, the stack thermally bonded to at least the heatproducing electrical components and the optical mounting structure, eachof the graphite layers having a plane high thermal conductivity along afirst axis and a lower thermal conductivity along a second axis, thestack having a three-dimensional shape including a length and a widthwhere the length is longer than the width and the first axis alignsparallel to said length, the stack having a height less than the width.8. The display of claim 7 wherein the bonded stack of graphite layers iscomprised of a plurality of sheets of pyrolytic graphite.
 9. The displayof claim 8 wherein the bonded stack is embedded in a material formedinto the optical mounting structure.
 10. The display of claim 8 whereinthe length is defined by a first end and a second end, the first endcoupled to the heat producing electrical components, the second endextending away from the heat producing components and bonded to anexterior surface of the optical mounting structure.
 11. The display ofclaim 8 wherein the stack of graphite layers comprises a plurality ofgraphite sheets and a plurality of bonding layers interspersed betweenthe graphite sheets, each one of the bonding layers comprising a metal.12. The display of claim 8 wherein the stack of graphite layerscomprises a plurality of graphite sheets and a plurality of bondinglayers interspersed between the graphite sheets, each one of the bondinglayers comprising an adhesive.